1. Field
The exemplary embodiments generally relate to synthetic jets and, more particularly, to driving and monitoring synthetic jet generators. The advantageous embodiments also relate generally to decreasing the effects of drag of a jet as it leaves an aperture.
2. Background
Actuators of a synthetic jet generator are generally driven with a sinusoidal input at a frequency that generates an optimum jet velocity based on the frequency response of the synthetic jet generator. Determining the frequency that results in optimum flow generally requires a calibration routine using an external sensor, for example, an accelerometer. External sensors that have a proper size, noise floor, dynamic range, and robustness for synthetic jet generator applications are generally expensive, typically costing more than the synthetic jet generator itself. The external sensors are generally intrusive and are not conducive to in-situ measurements of the synthetic jet generator.
In the event that the frequency response of the synthetic jet generator shifts, due to structural changes in the generator or environmental conditions, re-characterization of the synthetic jet generator generally requires at least re-attaching an external sensor and re-executing the calibration routine. In certain applications, for example, when the generator is attached to a wing in flight, re-characterization may be prohibited. Furthermore, determining if the synthetic jet generator has degraded and is approaching a failure condition is not feasible without dismantling the generator from its application and returning the generator to a test bed where the external sensor may be attached, and the calibration routine re-executed.
It would be advantageous to be able to characterize a synthetic jet generator without using a calibration routine and a costly external sensor. It would also be advantageous to tune a driving frequency of the synthetic jet generator to maintain the optimum jet velocity, or optimum flow and to determine if the synthetic jet generator is approaching a failure condition.
In addition, a limit on the velocity of the jet is damping induced by drag of the fluid as it emerges from an aperture in the synthetic jet generator. This drag is the primary cause of damping at the resonant frequency at which the jet operates. It would be advantageous to decrease the damping caused by drag and thereby increase the velocity of the jet emerging from the aperture.